org.elasticsearch.ingest.common.AppendProcessorTests.testCopyFromOtherField very very rare failure

[joegallo]

CI Link

https://gradle-enterprise.elastic.co/s/ibujerii6cnqu

Repro line

./gradlew ":modules:ingest-common:test" -Dtests.iters=10000 -Dtests.failfast=true --tests "org.elasticsearch.ingest.common.AppendProcessorTests"

Does it reproduce?

Yes

Applicable branches

main

Failure history

No response

Failure excerpt

./gradlew ":modules:ingest-common:test" -Dtests.iters=10000 -Dtests.failfast=true --tests "org.elasticsearch.ingest.common.AppendProcessorTests"
[... so much output ...]
2> REPRODUCE WITH: ./gradlew ":modules:ingest-common:test" --tests "org.elasticsearch.ingest.common.AppendProcessorTests.testCopyFromOtherField {seed=[DAFB357964D00301:C2D44A33368AEFE1]}" -Dtests.seed=DAFB357964D00301 -Dtests.locale=ca-Latn-ES -Dtests.timezone=Australia/Darwin -Druntime.java=25
2> java.lang.IllegalArgumentException: path [񓛓񪱓󆖀𝇆򋄬󸂍󋆘񅚛..񮝈󍑯𶥆򁐢𑍑򇍞󰱗󯏏򭶅.EswfMbbSHE.ZY] is not valid
at __randomizedtesting.SeedInfo.seed([DAFB357964D00301:C2D44A33368AEFE1]:0)
at org.elasticsearch.ingest.IngestDocument$FieldPath.validateClassicFields(IngestDocument.java:1391)
at org.elasticsearch.ingest.IngestDocument$FieldPath.processPathParts(IngestDocument.java:1376)
at org.elasticsearch.ingest.IngestDocument$FieldPath.(IngestDocument.java:1371)
at org.elasticsearch.ingest.IngestDocument$FieldPath.of(IngestDocument.java:1345)
at org.elasticsearch.ingest.IngestDocument.setFieldValue(IngestDocument.java:754)
at org.elasticsearch.ingest.IngestDocument.setFieldValue(IngestDocument.java:694)
at org.elasticsearch.ingest.RandomDocumentPicks.addRandomField(RandomDocumentPicks.java:108)
at org.elasticsearch.ingest.common.AppendProcessorTests.testCopyFromOtherField(AppendProcessorTests.java:335)
2> NOTE: leaving temporary files on disk at: /Users/joegallo/Code/elastic/elasticsearch/modules/ingest-common/build/testrun/test/temp/org.elasticsearch.ingest.common.AppendProcessorTests_DAFB357964D00301-001
2> NOTE: test params are: codec=Asserting(Lucene103): {}, docValues:{}, maxPointsInLeafNode=26, maxMBSortInHeap=5.134741186584475, sim=Asserting(RandomSimilarity(queryNorm=true): {}), locale=ca-Latn-ES, timezone=Australia/Darwin
2> NOTE: Mac OS X 15.7.1 aarch64/Oracle Corporation 25 (64-bit)/cpus=12,threads=1,free=288959000,total=536870912
2> NOTE: All tests run in this JVM: [AppendProcessorTests]

Tests with failures:

• org.elasticsearch.ingest.common.AppendProcessorTests.testCopyFromOtherField {seed=[DAFB357964D00301:C2D44A33368AEFE1]}

130000 tests completed, 1 failed, 81705 skipped

Task :modules:ingest-common:test FAILED

FAILURE: Build failed with an exception.

• What went wrong:
  Execution failed for task ':modules:ingest-common:test'.

There were failing tests. See the report at: file:///Users/joegallo/Code/elastic/elasticsearch/modules/ingest-common/build/reports/tests/test/index.html

BUILD FAILED in 1m 15s
100 actionable tasks: 1 executed, 99 up-to-date

Publishing Build Scan...
https://gradle-enterprise.elastic.co/s/ibujerii6cnqu

[elasticsearchmachine]

Pinging @elastic/es-data-management (Team:Data Management)

[joegallo]

I mentioned this on #136687, and this is me following up on creating an issue for it.

[seanzatzdev]

hm i'm not able to reproduce with the same seed for some reason:

➜  elasticsearch git:(main) ./gradlew ":modules:ingest-common:test" --tests "org.elasticsearch.ingest.common.AppendProcessorTests.testCopyFromOtherField" -Dtests.seed=DAFB357964D00301 -Dtests.locale=ca-Latn-ES -Dtests.timezone=Australia/Darwin -Druntime.java=25
=======================================
Elasticsearch Build Hamster says Hello!
  Gradle Version        : 9.1.0
  OS Info               : Mac OS X 15.7.1 (aarch64)
  Runtime JDK Version   : 25+36-3489 (Oracle, 25+36-3489)
  Runtime java.home     : /Users/seanzatz/.gradle/jdks/oracle_corporation-25-aarch64-os_x.2/jdk-25.jdk/Contents/Home
  Gradle JDK Version    : 21.0.7+6-LTS (Eclipse Temurin)
  Gradle java.home      : /Users/seanzatz/.gradle/jdks/eclipse_adoptium-21-aarch64-os_x.2/jdk-21.0.7+6/Contents/Home
  Random Testing Seed   : DAFB357964D00301
  In FIPS 140 mode      : false
=======================================

> Task :modules:ingest-common:test
WARNING: module-info.class ignored in patch: /Users/seanzatz/workspace/elasticsearch/libs/entitlement/bridge/build/distributions/elasticsearch-entitlement-bridge-9.3.0-SNAPSHOT.jar

BUILD SUCCESSFUL in 8s
100 actionable tasks: 1 executed, 99 up-to-date
Consider enabling configuration cache to speed up this build: https://docs.gradle.org/9.1.0/userguide/configuration_cache_enabling.html

but i reproduced here:

1> [2025-10-17T07:05:23,431][INFO ][o.e.i.c.AppendProcessorTests][testAppendValuesToExistingList] [seed=[622839918FFAD261:E8D31C04FD5E16CA]] after test
  2> REPRODUCE WITH: ./gradlew ":modules:ingest-common:test" --tests "org.elasticsearch.ingest.common.AppendProcessorTests.testAppendValuesToExistingList {seed=[622839918FFAD261:E8D31C04FD5E16CA]}" -Dtests.seed=622839918FFAD261 -Dtests.locale=sa -Dtests.timezone=Pacific/Kanton -Druntime.java=25
  2> java.lang.IllegalArgumentException: path [𹡹.MC..񗃹𝮠𚰉񈌇򂦕򆿰.7VQ] is not valid
        at __randomizedtesting.SeedInfo.seed([622839918FFAD261:E8D31C04FD5E16CA]:0)
        at org.elasticsearch.ingest.IngestDocument$FieldPath.validateClassicFields(IngestDocument.java:1412)
        at org.elasticsearch.ingest.IngestDocument$FieldPath.processPathParts(IngestDocument.java:1397)
        at org.elasticsearch.ingest.IngestDocument$FieldPath.<init>(IngestDocument.java:1392)
        at org.elasticsearch.ingest.IngestDocument$FieldPath.of(IngestDocument.java:1366)
        at org.elasticsearch.ingest.IngestDocument.setFieldValue(IngestDocument.java:754)
        at org.elasticsearch.ingest.IngestDocument.setFieldValue(IngestDocument.java:694)
        at org.elasticsearch.ingest.RandomDocumentPicks.addRandomField(RandomDocumentPicks.java:108)
        at org.elasticsearch.ingest.common.AppendProcessorTests.testAppendValuesToExistingList(AppendProcessorTests.java:50)
  2> NOTE: leaving temporary files on disk at: /Users/seanzatz/workspace/elasticsearch/modules/ingest-common/build/testrun/test/temp/org.elasticsearch.ingest.common.AppendProcessorTests_622839918FFAD261-001
  2> NOTE: test params are: codec=Asserting(Lucene103): {}, docValues:{}, maxPointsInLeafNode=774, maxMBSortInHeap=6.044067774802311, sim=Asserting(RandomSimilarity(queryNorm=true): {}), locale=sa, timezone=Pacific/Kanton
  2> NOTE: Mac OS X 15.7.1 aarch64/Oracle Corporation 25 (64-bit)/cpus=12,threads=1,free=425678512,total=536870912
  2> NOTE: All tests run in this JVM: [AppendProcessorTests]

it seems like an issue with the path having empty segments